Circuit interrupter grid structure for oil-break circuit interrupter

ABSTRACT

An oil-type circuit breaker has three poles provided in a unitary tank structure, each pole comprising a pair of serially related grid structures. The grid structures are constructed by nesting a plurality of plate elements, constituting vent passages and oil pockets, within an outer cylindrical glass-filament-wound shell. The stationary contact assembly is so arranged as to have a lengthened finger, which serves as an arcing horn disposed adjacent side lateral vent openings. The vent openings are formed by molded vent elements of particular materials and having a splitter plate interposed therebetween. Additional oil pockets and a lower oil-pocket plug, having an entrance opening, assist in guiding the movable contact rod, and additionally providing considerable turbulence within the oil during the opening operation.

United States Patent Hess et al.

[54] CIRCUIT INTERRUPTER GRID STRUCTURE FOR OIL-BREAK CIRCUITINTERRUPTER [72] inventors: Robert L. I-less, E. McKeesport; Gerald D.

Summers, Greensburg, both of Pa.

[73] Assignee: Westinghouse Electric Corporation, Pittsburgh, Pa.

22] Filed: ',Feb. 6, 1968 21 ,Appl. No.: 703,410

[52] U.S.Cl. ..20l)/l50 R, ZOO/150E [51] Int. Cl. ..H0lh 33/68 [58]Field of Search ..200/l50 F, 150.2, 150

[56] References Cited UNITED STATES PATENTS 2,760,033 8/1956 MacNeil etal. ..200/ 150 3,128,360 4/1964 Rieti 200/150 3,214,550 10/1965 Easley200/150 X 3,335,245 8/1967 McCloud ..200/150 3,356,811 12/1967 Cushinget al. ..200/150 3,392,248 7/1968 Rietz et a1 ..200/150 1 Feb. 29-, 1972FOREIGN PATENTS OR APPLICATIONS 1,143,891 2 /1963 Germany 200/15O OTHERPUBLICATIONS lTE Circuit Breaker Company Bulletin No. 2031A; March,1960;

Primary Examiner-Robert K. Schaefer Assistant Examiner-Robert A.Vanderhye Attorney-A. T. Stratton, C. L. McHale and W, R. Crout 5 71ABSTRACT An oil-type circuit breaker has three poles provided in aunitary tank structure, each pole comprising a pair of serially relatedgrid structures. The grid structures are constructed by nesting aplurality of plate elements, constituting vent passages and oil pockets,within an outer cylindrical glass-filament-wound shell. The stationarycontact assembly is so arranged as to have a lengthened finger, whichserves as an arcing horn disposed adjacent side lateral vent openings.The vent openings are formed by molded vent elements of particularmaterials and having a splitter plate interposed f'therebetween.Additional oil pockets and a lower oil-pocket plug, having an entranceopening, assist in guiding the movable contact rod, and additionallyproviding considerable turbulence within the oil during the openingoperation.

13 Claims, 12 Drawing Figures Patented Feb. 29, 1972 4 Sheets-Sheet lPatented Feb. 29, 1972 3,646,296

4 Sheets-Sheet 2 FIG. IO.

Patented Feb. 29 1972 4 Sheets-Sheet 3 FIG. 3.

FIG. 4.

CIRCUIT INTERRUPTER GRID STRUCTURE FOR OIL- BREAK CIRCUIT INTERRUP'IERBACKGROUND OF THE INVENTION As well known by those skilled in the art,it has been common practice heretofore to provide separate tankstructures for circuit interrupters of intermediate voltage rating. Thishas necessitated a considerable cost expenditure for the separate tankunits and, additionally, the necessity of providing linking mechanismfor interrelating the movable contact structures within the several tankunits. It is, therefore, preferable to provide the three pole-unitswithin a single tank structure, thereby reducing the cost andsimplifying the linkage for the operating mechanism. To provide such aconstruction for the same intermediate voltage levels, it is, of course,necessary to provide a highly efficient arc-interrupting grid structureof relatively small size and highly efficient operation. Moreover, itis'necessary to prevent external flashover on the outer surfaces of thegrid units by so directing the exhaust gases as to prevent theircombination from the several spaced grid structures.

As typical of prior art constructions, reference may be had to U.S. Pat.application Ser. No. 425,728, filed Jan. I5, 1965, now US. Pat. No.3,356,811, issued Dec. 5, 1967 to George B. Cushing and Frank L. Reese,and assigned to the assignee of the present invention, which exemplifiesa prior art structure. According to the present invention, thedimensions have been reduced and the grid elements have been improved,with improved venting channels of constant cross-sectional area, andwith oil pockets of such configuration and location, as to providehighly efficient oil grid units, and to enable the radially spaceddisposition of six such units within a single tank, thereby permittingthe three pole-units, for a three-phase con struction, to be disposedwithin a single unitary tank structure.

SUMMARY OF THE INVENTION According to a preferred embodiment of theinvention, there are provided six grid structures within a single tankhaving their individual vents directed radially outwardly to preventexternal flashover. Each of the six grid units comprises a nesting ofseveral grid elements within an outer cylindrical glass-filament-woundshell, having an upper insert, which enables its ready assemblage to athreaded contact foot. By the use of venting channels and suitablylocated oil pockets provided by elements of unique composition, a highlyfavorable arrangement, including gas evolution and oil turbulence, isachieved to result in a highly efficient grid unit of reduceddimensions. As a result, not only are the three poles provided in asingle tank, but, additionally, the dimensions of all the elements arereduced and the structure thereby made more lightweight in construction.

Additionally, there is provided a pair of vent channels having asplitter plate interposed therebetween to encourage arc looping into thevent channels and to prevent its physical ejec tion externally of thegrid casing.

A general object of the present invention is, accordingly, to provide animproved oil-break grid structure for a circuit interrupter of highlyefficient operation and of reduced dimen- SIOIIS.

Still a further object of the present invention is to provide animproved oil grid structure, in which a few of the several insulatingelements are provided, such as by molding, from particular resinousmaterials.

Still a further object of the present invention is the provision of alow-cost, rapidly assembled grid structure, which is highly efficient inoperation and of reduced dimensions.

Further objects and advantages will readily become apparent upon readingthe following specification, taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a vertical sectional viewtaken through a three-pole oil-type circuit interrupter embodying theprinciples of the present invention, the contact structure beingillustrated in the closed-circuit position;

FIG. 2 is a plan view, the line IIII of FIG. 1;

FIG. 3 is a considerably enlarged vertical sectional view taken throughthe interior of one of the oil grid units, the contact structure beingillustrated in the closed-circuit position;

FIG. 3a is a fragmentary view, somewhat similar to that of FIG. 3, butillustrating the disposition of the several parts, and the arc location,during an intermediate part of the opening operation;

FIG. 4 is an end elevational view of the oil grid structure of FIG. 3;

FIG. 5 is an inverted plan view of the contact housing of FIG. 3, takenin the direction of the arrows V-V of FIG. 3;

FIG. 6 is a top plan view of one ofthe venting elements;

FIG. 7 is an end elevational view of the venting element of FIG. 6;

FIGS. 8 and 9 are vertical sectional views taken through the bottom andtop molded venting plates respectively;

FIG. 10 is a vertical sectional view taken through the lower insulatingmolded plug element of the oil grid; and,

FIG. 11 is a top plan view of the lower plug element of FIG. 10.

in section, taken substantially along DESCRIPTION OF THE PREFERREDEMBODIMENT Referring to the drawings, and more particularly to FIGS. 1and 2 thereof, it will be noted that there is provided a threephaseoil-type circuit interrupter l adaptable for intermediate voltageratings, such as 34.5 kv., for example, and say, for example, having acurrent rating of l,200 amperes. As illustrated in FIG. 2, the threepole-units A, B and C are disposed within a single tank structure 2.Reference may be had to the sectional view of FIG. 2 for an illustrationof the manner of disposition and electrical interconnection of the threepole-units A, B and C within the tank 2.

It will be apparent that each of the oil grid units 4 is clamped to, andfixedly secured to, the lower ends 5 of the terminal bushing studs 6extending through the upper cover 7 of the tank 2. Current transformers8 may surround the terminal bushings 9 beneath the cover 7 for relayingcircuits.

With reference to FIG. 2, it will be observed that, generally, eachpole-unit A, B or C comprises a pair of serially related grid structures4, which are electrically interconnected by conducting crossarms 11A,11B, or 11C, which are reciprocally vertically moved, in an opening andclosing direction, by lift rods 12A, 128 or 12C. Three such lift rods12A, 12B and 12C are provided and are mechanically interconnected to thelinkage mechanism disposed at the upper end of the tank structure 2.

FIG. 3 more clearly illustrates the internal construction of the gridstructure 4. Generally, it will be noted that there is provided an outercylindrical insulating shell 14 formed of a suitable insulatingmaterial, such as gIass-filament-filled epoxy resin, and having theseveral grid elements disposed therein, as more fully explainedhereinafter.

A split casting 15, serving as a contact foot, is threaded, as

a at 15a, onto each bushing stud 6. Bolted to this contact foot 15 is acast stationary contact finger housing I7. Between these two components15, 17 is inserted a cast bevel ring 19, that seats flat, as at 19a(FIG. 3), against the contact foot 15 and into a bevel seat 17a on thetop of the finger housing 17. With this arrangement, lateral and pivotaladjustment is possible during contact and interrupter alignment.

Four finger contacts 21, mounted on a finger block 22, make up thestationary contact cluster 24, that is bolted in the finger box 17. Eachfinger 21 is a Cupaloy, or copperchromium alloy forging fitted with anarc-resistant tungstensilver alloy tip 21a. One of the fingers 24A isfive-sixteenths inch longer than the other three, for example. When thebreaker 1 opens, the long finger 24A is the last to separate with themoving contact 26, thus acting as an arc horn for protecting the othercontact surfaces from burning. All four fingers 21 are spring loaded, asat 27. to provide the proper contact pressure against the rod-typemoving contact 26 and the stationary finger block 22 in the closedposition, as shown in FIG. 3. The resulting rocker-type action of thefour fingers 21 eliminates shunting of the four fingers 21 to the fingerblock 22.

Mounted below the stationary contact-finger box 17 is the interruptingportion 4A of the interrupter grid 4. The grid portion 4A is composed ofa stack of insulating elements of various compositions housed within a4-inch inside diameter, for example, glass-filament-wound shell 14 ofthe voltage rating considered. The grid assembly is threaded onto thefinger box 17 by means of an aluminum insert 1411, which is incorporatedand interlocked in the shell 14 during the actual glass-filament-windingprocess. When correct alignment is achieved, a small bolt 28, threadedinto a lug 29 on the finger box 17, is tightened against the machinedtopsurface 146 of the tube 14 locking it in place.

The projection 30 of the arc-horn finger 24A down into the apertures 31,32 in the top two fiber plates 33, 34 of the grid stack 4 make itnecessary to mount these two plates 33, 34 on the finger box 17 withretaining screws 35. The remainder of the stack elements are inserteddirectly into the glass-filamentwound shell 14, and mate with the toptwo fiber plates 33, 34 when the shell 14 is threaded onto the fingerbox 17. The third and fifth plates 36, 37 in the grid are each 0.75-inchthick, for example, and injection molded of glass-reinforced Celcon" orDelrin.

Celcon" and .Delrin" are high molecular weight polyoxymethylenematerials. They are both thermoplastic resins. Delrin" is commerciallyavailable from E. I. du Pont Company and Celcon" from the CelaneseCorporation. For details of preparation of suitable polyoxymethylenes,reference may be had to U.S. Pat. No. 3,027,352 and U.S. Pat. No.2,768,994.

In combination with the fourth plate 39, a splitter made fromone-fourth-inch thick, for example, fiber sheet, the group forms thevent channels 41, 42 for the grid 4. Snouts or projections 36a, 37a onthese three vent elements extend through a hole 44 bored into thesidewall of the giass-filamentwound tube 14. This arrangement provides apositive alignment of the vent channels 41, 42 of the stack with thehole 44 in the shell 14. Correct alignment of the vent plates 36, 37 andsplitter plate 39 is further insured by two small bosses, on each of themolded vent plates 36, 37 that fit into punched holes provided in thesplitter plate 39.

By molding the vent plates 36, 37 a unique, constant cross sectionchannel configuration was made possible that would keep the bored hole44 in the filament-wound shell 14 to a minimum size, thus sacrificing aminimum in tube strength 14. In each item, the channel is 0.5-inch highby 0.75-inch wide, for example, with a 0.06-inch radius at the comers Xat the inside end, providing a desired flow area for gasses formedduring arcing. From the arcing end X" to the exhaust end Y (FIG. 9) ofthe channels 41, 42, the corners blend from the 0.06-inch radius to a0.34-inch radius, thereby maintaining the same cross-sectional vent areathroughout the channels 41,42. The channel height at the exhaust end Y"is reduced to 0.34-inch high, for example, allowing for the small exithole 44 in the filament-wound shell 14.

The rear portion 36b, 37b of each vent plate 36, 37 is a large cavity,that forms a separate oil pocket when assembled in the filament-woundshell 14.

The sixth, seventh, ninth and th plates 46, 47, 49, 50 in the grid 4 aresimple 0.25-inch thick punched round fiber plates, for example, with a1.06-inch diameter clearance hole 53 in their center for the movingcontact 26. These plates add strength to the inner construction of theinterrupter 4 and form oil pockets 55, 56 with the plates above andbelow them. Variations in fiber thickness, which ultimately affect thegrid stack height, are compensated for by substituting, or adding0.l88-inch thick fiber plates of the same design for these plates. Adimensional check of the interrupter stack can be made before assemblyin the shell 14.

The eighth element 48 is more a spacer than a plate. It is machined frompolyvinyl chloride resin pipe to fit snugly within the filament-woundshell 14. Bounded by the above fiber plates 46, 47, it forms the largestoil pocket 55 in the interrupter 4.

Proper compression of the grid stack plates is accomplished with the11th, 12th and 13th plates 58-60. They are, in essence, threecork-neoprene washers, that compress between the flat fiber plate 50 andthe bottom plug 62 when the interrupter 4 is threaded onto the fingerbox 17.

The bottom plate 62 in the interrupter 4 is unique in that it is alsoinjection-molded of glass-reinforced Celcon." In its design areincorporated many functions. It serves as a plug for the open-endedfilament-wound shell 14, seating on a chamfered shelf 14c, that isintegrally wound into the shell 14. The fiat cork-neoprene washers58-60, that seat on this plug 62, encircle a cylindrical section 62a ofit, that acts as a stop for the stack when compressed during assembly.In the center of the plug 62 is a tapered entrance hole 62b for themoving contact 26 that assures its proper entry and alignment. An innercavity 620 in the .Celcon plug 62 forms the lowermost oil pocket 56 inthe grid stack 4. I 1

The assembly of the interrupter grid 4 is somewhat in reverse order,than as described above. All of the plates are assembled in thefilament-wound shell 14 from the threaded insert upper end, startingwith the molded Celcon" bottom plug 62. The simple design used in theconstruction of this interrupter 4 provides a unit that is easy toassemble, inspect and maintain.

By way of recapitulation, during the opening operation, the mechanicallinkage, disposed adjacent the upper end of the tank 2, causes downwardopening movement of the three liftrods 12A, 12B and 12C. This downwardopening motion of the three lift-rods causes corresponding downwardopening movement of the three conducting crossbars 11A, 11B and 11C. Theseveral, rod-shaped moving contacts 26 move downwardly away from thestationary contacts 24, and cause the establishment of arcs 25 betweenthe arcing finger contacts 24A and the tip portions 26a of the movingcontacts 26. FIG. 3A illustrates more clearly the arc establishment,wherein the arc 25 is carried by the explosive action of the oil andvapor out through the lateral vent channels 41, 42 causing the are 25 topass through the aperture 39a provided in the splitter plate 39. Thishole 39a in the splitter plate 36 stabilizes the arc position, andpermits the two looped portions 25a, 25b of the are 25 to move somewhatlaterally out of the vent channels 41, 42 to receive the full lateralthrust of the oil and gas flow externally of the grid unit 4. Theprovision of the oil venting pockets 36b, 37b and 55 maintains aplentiful supply of oil 3 adjacent the path of movement of the movingcontact 26, and causes the vaporization of the oil within these pockets.If the are 25 has not been interrupted by the time that it passesthrough the apertures 53 of the plates 49 and 50, it encounters anadditional oil pocket 56 adjacent the lower end of the grid structure 4.This will cause an upward and a downward flow of oil along the path ofmovement of the moving contact 26 to further intensify the extinction ofrelatively low-amperage arcs. By the time that the moving contact 26 hascleared the lower opening 62b of the lower venting plug 62, areextinction has definitely occurred, and further downward openingmovement provides a plurality of isolating gaps in the circuit, as shownby the chain lines 40 in FIG. 1.

During the closing operation, the operating mechanism linkage causesupward closing travel of the lift rods 12A, 12B and 12C. This causescorresponding upward movement of the conducting cross-arms 11A, 11B and11C, thereby causing the several moving contacts 26 to come into closedcontacting engagement with the stationary contact structures 24, thuscompleting the circuit through the interrupting device 1.

From the foregoing description, it will be apparent that there has beenprovided a novel oil-break grid interrupting structure 4 incorporatingconfigured grid elements of unique shape, and providing a highlyefficient extinguishing function. As a result, the dimensions have beenreduced, and the three pole-units A, B and C may be disposed within asingle tank structure 2, with the venting channels 41, 42 directedradially outwardly within the tank 4 to prevent comingling of the arcgases thereby preventing interphase flashover.

Although there has been illustrated and described a specific structure,it is to be clearly understood that the same was merely for the purposeof illustration, and that changes and modifications may readily be madetherein by those skilled in the art, without departing from the spiritand scope of the invention.

We claim as our invention: 1

l. A liquid-break type of circuit interrupter including a tankstructure, a grid unit having a relatively stationary contact disposedadjacent its upper end, a terminal bushing extending into said tankstructure and supporting said grid unit adjacent its lower end, liquiddisposed in said tank structure and submerging said grid unit, platestructure disposed interiorly within said grid structure, afunnel-shaped molded plug member of resinous material located at thelower end of said grid unit and having a reentrant wall portion todefine a liquid pocket and a central opening therethrough, and arod-shaped movable contact movable through said central opening intoengagement with said relatively stationary contact during the closingoperation.

2. The combination of claim 1, wherein the grid unit comprises a tubehaving a lower inclined supported shelf portion, and the funnel-shapedmolded plug member having a radially outwardly extending beveled portionseating on the aforesaid shelf portion.

3. The combination according to claim 1, wherein the funnel-shapedmolded plug member is formed of a thermoplastic resinous material.

4. The combination of claim 3, wherein the thermoplastic resinousmaterial is a high molecular weight polyoxymethylene material.

5. In a liquid-break type of circuit interrupter, in combination, a tankstructure having a terminal bushing having a terminal stud passingtherethrough and extending into said tank structure, a contact footsecured to the lower end of the terminal stud, a stationary contacthousing secured to the lower side of the contact foot, an insulatinginterrupter shell secured to the stationary contact housing, a pluralityof separate insulating elements nested within the insulating interruptershell, at least one of the elements providing a lateral venting channelextending laterally out an opening in the sidewall of said shell, andthe same cross-sectional venting area existing throughout the ventingchannel.

6. The combination according to claim 5, wherein two molded elementsprovide venting channels extending out of the insulating shell, asplitter plate extending between said elements, and the samecross-sectional venting area existing throughout the venting channelsprovided by said venting elements.

7. The combination of claim 1, wherein resilient ringshaped meanscompresses the plate structure during assembly.

8. The combination of claim 7, wherein the resilient ringshaped meanscomprises one or more washer plates comprising neoprene material.

9. The combination of claim 1, wherein the plate structure comprises oneor more molded members having integrally molded generally U-shapedvent-forming portions which extend out a-hole in an enclosing tubestructure.

10. The combination of claim 9, wherein two such members are providedwith a splitter plate disposed therebetween.

11. The combination of claim 9 wherein the cross-sectional area of theventing channels is constant.

12. The combination of claim 10, wherein the cross-sectional area of thetwo venting channels is constant.

13. An oil grid unit comprising an outer tube having an opening throughthe sidewall thereof, spaced vent-forming molded members ofthermoplastic material having generally U-shaped venting portions, anintervening splitter plate disposed between said molded members andextending through said hole, means for establishing an arc within saigrid unit, whereby the oil and gas is ejected out of the two ventingchannels, and the cross-sectional area of the venting channels beingconstant.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORREC'HON Patent No. 3,6l6,296 Dated 29 February 1972 Inv entor(s) Robert L. Hess and Gerald D.Simmers It is certified that error appears in the above-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

[72] should read "Robert L. Hess, E. McKeesport; Gerald D.

simmers Greensburg, both of Pa."

Signed and sealed this 9th. day of January 1973* (SEAL) Attest:

I EDWARD M. FLETCHER,JR. ROBERT GOTTSCHALK Attesting OfficerCommissioner of Patents FORM powso uscoMM-oc scan-Pee i 11,5. GOVERNMENTPRINTING OFFICE: IOII 0-800-"1 DNl'lED STATES PArENr ormbs QETEFEQATE F@EQTKN Patent No. 3,6 46 ,296 Dated 29 February 1972 Inventor(s) RobertL. Hess and Gerald D. Simmers It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

[72] should read "Robert L. Hess, E. McKeesport; Gerald D.

simmers, Greensburg, both of Pa."

Signed and sealed this 9th day of January 1973 (SEAL) Attest:

EDWARD M.PLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissionerof Patents FORM P0-1050 uscoMM-oc 6037u-pe9 U,S. GOVERNMENT PRINTINGOFFICE I019 O-JOi-SSl

1. A liquid-break type of circuit interrupter including a tankstructure, a grid unit having a relatively stationary contact disposedadjacent its upper end, a terminal bushing extending into said tankstructure and supporting said grid unit adjacent its lower end, liquiddisposed in said tank structure and submerging said grid unit, platestructure disposed interiorly within said grid structure, afunnel-shaped molded plug member of resinous material located at thelower end of said grid unit and having a reentrant wall portion todefine a liquid pocket and a central opening therethrough, and arod-shaped movable contact movable through said central opening intoengagement with said relatively stationary contact during the closinGoperation.
 2. The combination of claim 1, wherein the grid unitcomprises a tube having a lower inclined supported shelf portion, andthe funnel-shaped molded plug member having a radially outwardlyextending beveled portion seating on the aforesaid shelf portion.
 3. Thecombination according to claim 1, wherein the funnel-shaped molded plugmember is formed of a thermoplastic resinous material.
 4. Thecombination of claim 3, wherein the thermoplastic resinous material is ahigh molecular weight polyoxymethylene material.
 5. In a liquid-breaktype of circuit interrupter, in combination, a tank structure having aterminal bushing having a terminal stud passing therethrough andextending into said tank structure, a contact foot secured to the lowerend of the terminal stud, a stationary contact housing secured to thelower side of the contact foot, an insulating interrupter shell securedto the stationary contact housing, a plurality of separate insulatingelements nested within the insulating interrupter shell, at least one ofthe elements providing a lateral venting channel extending laterally outan opening in the sidewall of said shell, and the same cross-sectionalventing area existing throughout the venting channel.
 6. The combinationaccording to claim 5, wherein two molded elements provide ventingchannels extending out of the insulating shell, a splitter plateextending between said elements, and the same cross-sectional ventingarea existing throughout the venting channels provided by said ventingelements.
 7. The combination of claim 1, wherein resilient ring-shapedmeans compresses the plate structure during assembly.
 8. The combinationof claim 7, wherein the resilient ring-shaped means comprises one ormore washer plates comprising neoprene material.
 9. The combination ofclaim 1, wherein the plate structure comprises one or more moldedmembers having integrally molded generally U-shaped vent-formingportions which extend out a hole in an enclosing tube structure.
 10. Thecombination of claim 9, wherein two such members are provided with asplitter plate disposed therebetween.
 11. The combination of claim 9wherein the cross-sectional area of the venting channels is constant.12. The combination of claim 10, wherein the cross-sectional area of thetwo venting channels is constant.
 13. An oil grid unit comprising anouter tube having an opening through the sidewall thereof, spacedvent-forming molded members of thermoplastic material having generallyU-shaped venting portions, an intervening splitter plate disposedbetween said molded members and extending through said hole, means forestablishing an arc within said grid unit, whereby the oil and gas isejected out of the two venting channels, and the cross-sectional area ofthe venting channels being constant.